The method of this invention relates to the preparation of a solid propellant grain that has high burning rate and good mechanical properties.
U.S. Pat. No. 1,455,309 issued to Archibald Jackson Strane on May 15, 1923 employs a mixture of black powder and nitrocellulose smokeless powder. U.S. Pat. No. 1,455,309 is directed to a loose bed of mixed grains, one of which is ground colloided nitrocellulose powder, the other grain being black blasting powder. These grains are only a mechanical mixture which has no physical properties such as tensile strength. The burning rate throughout the bed is not controlled by chemical means, but only by flame propagation through the bed at local pressure conditions.
The present invention pertains to a solid structure of a heterogenous blend with the components thereof being held in place without movement. During burning of the heterogenous blend the flame front moves through the structure as a plane wave. This invention relates to the method of preparation of a multimodal blend which is cured to yield a high burning rate solid propellant grain that has good mechanical properties.
A problem associated with very high rate propellants relates to the poor physical and mechanical properties which are not conductive for use in rocket motors, particularly in case bonded motors. These propellants (such as ultrafine ammonium perchlorate-carborane propellants) have low tensile strength which allows the propellant to tear and separate or they have high strength propellants (such as is characteristic of the polysulfide or other epoxide type propellants) with brittle properties which results in propellant cracking and debonding, particularly during temperature changes to low temperatures.
Advantageous would be a method which incorporates high burning rate with good physical properties in a finished propellant grain.
Therefore an object of this invention is to provide a method of achieving high burning rate solid propellant grains that also have good physical properties.
Another object of this invention is to provide a high burning rate solid propellant grain that has good physical properties.
A further object of this invention is to provide a high burning rate solid propellant grain having a controlled burning rate that is controlled by propagation of the plane wave through the grain.